fix(server): use kernel mutex to ensure single instance (#207)

WeaselIPCServer/WeaselServerImpl.cpp

@@ -118,10 +118,14 @@ DWORD ServerImpl::OnCommand(WEASEL_IPC_COMMAND uMsg, DWORD wParam, DWORD lParam)
 
 int ServerImpl::Start()
 {
-	// assure single instance
-	if (FindWindow(WEASEL_IPC_WINDOW, NULL) != NULL)
-	{
-		return 0;
+	std::wstring instanceName = L"(WEASEL)Furandōru-Sukāretto-";
+	instanceName += getUsername();
+	HANDLE hMutexOneInstance = ::CreateMutex(NULL, FALSE, instanceName.c_str());
+	bool areYouOK = (::GetLastError() == ERROR_ALREADY_EXISTS ||
+		::GetLastError() == ERROR_ACCESS_DENIED);
+
+	if (areYouOK) {
+		return 0; // assure single instance
 	}
 
 	HWND hwnd = Create(NULL);

include/WeaselIPC.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <WeaselCommon.h>
+#include <WeaselUtility.h>
 #include <windows.h>
 #include <functional>
 #include <memory>
@@ -168,21 +169,8 @@ namespace weasel
 	inline std::wstring GetPipeName()
 	{
 		std::wstring pipe_name;
-		DWORD len = 0;
-		GetUserName(NULL, &len);
-
-		if (len <= 0) {
-			return pipe_name;
-		}
-
-		std::unique_ptr<wchar_t[]> username(new wchar_t[len]);
-
-		GetUserName(username.get(), &len);
-		if (len <= 0) {
-			return pipe_name;
-		}
 		pipe_name += L"\\\\.\\pipe\\";
-		pipe_name += username.get();
+		pipe_name += getUsername();
 		pipe_name += L"\\";
 		pipe_name += WEASEL_IPC_PIPE_NAME;
 		return pipe_name;

include/WeaselUtility.h

@@ -25,6 +25,26 @@ inline int utf8towcslen(const char* utf8_str, int utf8_len)
 	return MultiByteToWideChar(CP_UTF8, 0, utf8_str, utf8_len, NULL, 0);
 }
 
+inline std::wstring getUsername() {
+	DWORD len = 0;
+	GetUserName(NULL, &len);
+
+	if (len <= 0) {
+		return L"";
+	}
+
+	wchar_t *username = new wchar_t[len + 1];
+
+	GetUserName(username, &len);
+	if (len <= 0) {
+		delete[] username;
+		return L"";
+	}
+	auto res = std::wstring(username);
+	delete[] username;
+	return res;
+}
+
 // data directories
 std::wstring WeaselUserDataPath();